1. Field of the Invention
The present invention relates to an ink jet printing device which can expel a drop of ink and control the color intensity of said drop.
2. Description of the Prior Art
There is known in the field an ink jet printing device wherein the liquid is kept at a predetermined level in a small tube having its free end directed upwards (U.S. Pat. No. 3,179,042). Inserted in the tube are two electrodes located on the same horizontal plane, whereby they remain submerged under an ink layer of a predetermined thickness. The ink jet is generated by an instantaneous vaporization of the portion of ink inside the tube located between the two electrodes, so as to expel the ink layer upwards.
Also known is an ink jet printing device which electrically generates an agitated condition between an electrode and a counterelectrode, which in turn causes a plurality of ink particles to be emitted through the nozzle (U.S. Pat. No. 4,432,003). Another ink jet device uses a separate piezoelectric transducer to expel the drops after they have acted upon by an electrochemical means (U.S. Pat. No. 3,982,251).